Brush and brush holder for electric drills



3 Sheets-Sheet 1 F. COLLURA BRUSH AND BRUSH HOLDER FOR ELECTRIC DRILLSFiled April 24, 1945 Sept. 13, 1949,

T 7 \NVENTOR 1 fPAA CESCO 604401914 iTToRNx 5 SQQiL 133 19 590 F.@QLLURA BRUSH AND BRUSH HOLDER FOR ELECTRIC DRILLS 5 Sheets-Sheet 2Filed April 24:, 1945 v M FFWMQWJ ATTO R N E Sept. 13, 1949. F. COLLURA2,481,499

BilUSH AND BRUSH HOLDER FOR ELECTRIC DRILLS Filed April 24, 1945 3Sheets-Sheet 3 INVEN o R fzA/vaszrco 0440,64

Patented Sept. 13, 1949 UNITED STATES PATENT OFFICE.

BRUSH AND BRUSH HOLDER FOR ELEETRIC DRIELS Application April 24-, 1945,Serial" No; 590,079

9 Claims. 11

This invention relates to electric drills, orother' tools of a similarcharacter, supplied with ahand grip section in the nature of a pistolvgrip, the operators hand controlling the point of application of thedrill and the amount oipressureth-ere-L on: and also controllingtheelectric power switch sothat the power may be conveniently thrown on andoff.

An Object is the provision of an electric hand: tool having a minimumnumber of casin parts: sothat there are a minimum number of junctionlines on the casing, which: lines have the disadvantage of permittingentry of dust ancli other foreign matter, and also tend to. limit theefficiency of the tool by causing: discomfort or injury" to the hand ofthe operator along the. meeting lines of the casing, particularly attheliand' grip section.

A further object is the provision of a. Commit-'- tator and brushassembly in an electric tool: of. this type which permits readyassembly, removal; and replacement of brushes, provides a. brush subjectto a minimum of shearing, Wearing and? breaking strains, provides a.brush having acummutator contact surface which. functions with maximumefficiency and retains such. maximum; efficiency; and provides furthera. brush. having an. extended length. so that replacement is necessaryonly at longer intervals, while at the same. time the outsidedimensions: of. the. tool may be. sharply limited and the tool. renderedrelatively light and compact.

A further object is the provision of a commutator brush of a specialshape which permits maximum eifi-ciency at the commutator contact area,maximum efficiency because of the lengthof the brush and the massthereof available to take up frictional wear at contact, while at thesame time space necessary for the application of such brush in itsrelation to a. commutator is economi'zed and the feed. of such brushtoward the contact area to take upthe effects of contact wear may bereadily and: eili'ciently accomplished;

A. further object. is: the provision in. an electric tool of. a device;operating: the: on and off: power" switch,v of a nature such. that. itmaybe readily operated by one hand: of the operator so that the.- power'may bereadily. thrown.- orr by a.v finger of the. operators: hand.holding. the tool atthe hand; grip, While at the: same time: the samefinger; or a.v second finger of the; operator's: same hand; can; throwinto locking.- position a switch. lock: so; that: the power will:.remain on. without; theoperators; pressure: upon: the: switch. Thisswitch lock? may also; be; readily thrown, or: released; to: the u.m-

2. locking position, permitting the switch togo to the power-oftpositionso far as the lock isconcerned'.

Other obi'ects of the invention will in part be obvious and will in partappear hereinafter;

The invention accordingly comprises the fear tures of construction,combinations of elements; and arrangement of parts, which will beexemplifled in the constructions: hereinafter setforth, and the scope ofthe application of which will be indicated in the claims For a fullerunderstanding of the. nature and objectsof the invention referenceshould be had tothe following detailed description taken in 0011-nection with the accompanying drawings, in which:

Fig. 1 is a side elevation ofanassembled elec:-- trio drillemb'odyingthis invention;

Fig; 2- isa section on a somewhat enlargedscale on the lines 2-2 of Fig;i looking in thedirectiom orthe arrows,

Fig: 3 is a: section on the lines 3--3 of Fig; 2 looking inthe directionofthe arrows, this View" being on substantially thesame scale as Fig; 1and showing detailthebrush carrying unit as it isin position within thedrill:

Fig. 4 is a; detailshowing the en-d'cfthis brush carrying unit as it isbeing partly removed from the casing thereby permittingthe operation ofa brake which holds the brush inposition within the brush carrying unitWhile it is being removed from the-casing'a-nd thereafter:

Fig; 5 is a section taken on the line 5-5 of V Fig, Zbut drawn to thescale of Fig. 1;

1 the off. or no.-power position;

Fig. 9 is a sectionaldetail of one. of. the brush. carrying units;

Fig. 104s adetail. showing. the relation between, brush. aha-commutatorwith, an indication of the a passage of tangential line'sof; force,causedlby the contact between. the rotating. commutator anda the:brush,, through the: mass of the brush;

Fig; 1 1'. is a detail section showing azmodifiedr form: oftriggen'lock;

Figs 12*: is; a detail; showing. the; parts; of Fig. 1];

3 in section and in the unlocked position, on the lines |2-l2 of Fig.11;

Fig. 13 is a section looking in the direction of the arrows showing thisform of trigger lock in looking position;

Fig. 14 is a sectional detail showing a trigger lock such as that shownin Fig. 11 but with a spring tending to hold this look in non-lockingposition;

Fig. 15 is a section on the lines 15-45 of Fig. 14 looking in thedirection of the arrows; and

Fig. 16 is a side elevation of one of the brush carrying units showingthe brush as it is inserted in the holder ready to be moved in theholder to its operative position.

In the drawings, Fig. 1 shows a drill assembled in accordance with myinvention which comprises a main body section A having a central casingmember I and a pistol grip member 2 integrally connected therewith andforming part of a single casting which may be readily constructed ofmetal or aluminum. An end section B of the casing is connected to thesection A by the interposition of section C, provided with ventilatingpassages 3 leading to the interior of the tool. A drill chuck 4, brokenaway in its length for convenience of illustration, projects from theend of the casing section B.

A further casing section D is shown below the hand grip section I of themain casing and fitted thereto to complete the outside form of the tool.A switch trigger 5 and a projecting part of a lock therefor at 6 areshown. At 1 is shown the outer surface of a brush carrying unit fittedto an opening in the casing. A similar brush carrying unit 8 isindicated by dotted lines as provided on the opposite face of the toolcasing.

Referring now to Fig. 5 there is shown an electric motor having aconventional armature 9, field magnet I0 and windings therefor. Thisarmature carries a. central operating shaft [I journaled at 12 in casingA and I3 in casing C, and carrying at its outer end a pinion M whichoperates pinion IS on a stud shaft I6 carrying at its end a pinion l1meshing with the pinion l8 on the I brushes which constitute animportant feature of this invention. Referring first to Fig. 6, an upperbrush assembly unit is indicated at 8, removably held in position in theupper part of the tool casing by a screw 22 and carrying are shapedbrush 23, indicated as of usual carbon material, held within metallicholder 24 and having a contact area at 25 bearing upon the commutatorbars 26 and fed forward as it is worn away at the contact area by springpressure of the arm 2! bearing against the end of the brush, this armbeing the extended end of a coil spiral spring 28 suitably mounted uponstud 29 carried by the body of the unit 8.

The brush holder 24 has two parts, in addition to its main frame work, aback plate 24a, shown most clearly on Figs. 3, 9 and 16, and a frontplate 24b which is cut away in part as shown on Fig. 16 to provide anopen faced slot within which one end of the are shaped brush may beinserted from the side when the drill is in process of assembly or whenit is necessary to install a fresh brush. This makes it possible to usea comparatively long are shaped brush, providing a greater mass ofmaterial which will accordingly have a longer life and require lessfrequent replacement. As shown in Fig. 16, the brush is dropped into theopen faced slot and then moved in an anti-clockwise direction, carryingthe spring arm 27 with it and winding up the coil spring, until itreaches the position shown at Fig. 2 when it is ready for use. If itwere not for the provision of this holder thus formed with one sectioncut away so as to permit placing of the brush in the position shown inFig. 16, it would be possible to use only a comparatively short arebrush to the extent of the distance between the points marked a: and :con Fig. 16. It is found that with the construction as shown a brush maybe used well over the arc in length and up to a point of 270 and beyondin length. The 270 length of the arc is found quite serviceable anduseful. As shown on Figs. 2 and 6 the long are shaped brush thereillustrated is of a length such that while one end bears at its contactarea upon the commutator the other end approaches, as shown, thecommutator at a point along the circumference, and a relatively longbrush is thereby provided limited only by the practical length of abrush having one end at the contact area bearing upon the commutator andthe other end sufficiently spaced from the commutator so that the springarm 21 may be interposed as shown in Figs. 2 and 6. It will thus be seenthat the are shaped brush is struck upon a circle, the center of which,when the brush is installed, is outside the peripheral circumference ofthe commutator. The brush thus has a contact area at one end extendingradially across it While the mass of the brush extends away from saidcontact area along an are shaped line which may be extended so far asdesired up the point where further extension would bring its fartherend, and the feed spring bearing against it, too close to thecommutator. It will accordingly be seen that, while in some otherrelations the are shaped brush such as is shown would have a usefulfunction, independently of the construction of its holder, in thepresent relation, as shown, the shape of the brush is of specialimportance and the shape of the holder providing the cut away portionfor assembly of the brush is also of special utility.

A similar brush unit 1 is shown in Fig. 6 below the commutator removablyheld in place by screw 30 and carrying a brush, brush holder, andcontrolling spring therefor in all respects the same as that alreadydescribed for the upper brush.

This brush makes possible the use of a relatively large mass of brushmaterial, rendering replacements much less frequent, while at the sametime relatively small space is occupied by the brush and a smaller, morecompact tool is secured. In addition, the major tangential lines offorce caused by the friction between the brush and the oncoming rotaryarmature will as is indicated in Fig. 10 at 3|, pass through the body ofthe brush in the line of its path of movement rather than across suchline of movement as in brushes now in common use. This tends to lessenthe uneven wearing away of the brush at the line of contact with thecommutator and thereby to a marked extent increases the efficiency ofthe brush and lengthens its useful life. At the same time the wearingand shearing action between the brush and its holder are reduced to aminimum and particularly there is no excessive shearing action betweenthe brush and the holder at the end of the holder where the brush isforced against this end in a construction 5: new widely used: in, the.art; With. this; type; OI? brush: also all: ofv these: conditions.remain. sub.-

stantially. constant throu hout. the: life on; the:

vented; come in contact with the. armature: and;

damage would be caused. thereby;v Ii, provide a. stop: in the. nature ofa lug; 32; struck up: from the inner side of: the brush: holder 24; in.aposition. such that. the spring; arm. will,. at the appropriatetimetoward the end of its. trayeli be: caughtby this lug and be held: asagainst-inn ther' advances.

A form of electric tool in generalt use embodies. a straight brush with.a; spiral spring bearing again-st the end of such brush and: feeding it.forward to contact with. the commutator- This involves a shearing,breaking and crumbling ei. fectupon the lowerend of the brush. asalreadydescribed but it also involves. an: irregular erosiorr of the brush atthe contact area.- caused? by the fact that the feeding forward of? thespring is necessarily uneven and: the pressure of the brush on thecommutator at the contact area accordingly uneven. With: the presentconstruc tion, however, the spring pressure of" the arm-.- 21! upon theend of" the arc shaped brush is an even pressure exerted evenly; throughthe mass. of" the brush and: as a result. the erosive action at thecontact area is. substantially even and: the brush wears away evenlyand. with. maximum. efficiency.

With the brush assembly unit described; having a. spring pressure behindthe brushv tendin to. force it out. of." its container. the brush.would: be forced out by spring action as 7 911311115111 as? sembly unitis being removed: from. the casing:

and contact,v of brush. and commutator broken; To prevent this there isprovided. as; shown; in. Figs. 2, 3 and 4 a brake, inactive: when; the;brush, assembly unit is, in position within the; casingand brought into;action; as the; brush. assembl unit is removed from the casing.

As shown, this brake; is in-I the forms, of a lever 56.- pivoted; on,stud 51; carried, by the; brush. as sembly unit and formed at one. endat 5.8 to pass down through opening 59 in the containertrame; so thatit: may bear upon the; side; of; the brush 23. Sprin 6% bearing upon.the. other end 015 this brake lever tends normally to force it to.

braking; position. This brake lever is provided; at its. other endat 6!.with an inclined surface bearing upon the inclined projection 62 on;the: inner face of the. casing section. It: will thus: be seen that whenthe brush assembly unit, is; in position within the casing the brake;lever will be; held to the inactive position. against the force ofspring 58 as shown in Fig. 3, and that the; brush. may be freely fedforward in use. As how.- ever the brush assembly unit is being removedfrom the casing the end of thebrake lever passes away from theprojection 62 and: as shownin Fig. 4, spring 60 forces up the one end ofthe brake lever and the other braking and is; then brought into actionagainst the brush. to. hold it in position within the container andprevent its being forced out by the action of the, spring arm 21.

We come now to the switch for turning on andoffthe-power inv the use; ofthe tool. The under side of the hand grip section of the tool is closedby casing. section D... shown. as. ribbed to ra ns ev r: orrth swtchiriggen mthiscas the 6 limit. slipping ot the hand.. This section ofthe casing; carries a tube 33 through which passes the electric leadwires t4.- and 35; with contact posts; 36? and; 31. In; Fig. 5 switchlever 38- piv-. oted. at 39; and carrying an extended contact arm 40 is;shown. as; only in contact with the postv 36 and, power supply. to thetool is accordin ly'bmken; This. condition isnormally maintained byaction of; the spring 1:! acting against the; pivoted lever 38; to holdthe parts in: the; po-

sition: shown: in Fig. 5; When this lever 38 is turned; on its; pivotin. a clockwise direction, its arm; 40. will bridge the two. contacts.and power-- will? besupplied to the tool. Leads of the circuit. through,the motor and back are all such as; conventionally used in the art andare not, shown, in: detail; Posts. 56 and 51- as shown in Fig. 5; andat, the upper end, of' Fig- 8., supply connections for the ends of leadwire 58; and 59 connected in. conventional mannerfor driving the chuckrotating; motor. Soiar as this invention. is concerned; it is onlynecessary that; there be means for, switching on and ofi the; powerunder the: control of; a. spring-pressed switch; to; be operated; by thetrigger and trigger the. trigger 5; forward or to. the left. When it.

is. desired to. use the tool; the operator with his: hand on the handgrip section by the use of, for example. hisv second finger, presses inthe trigger 5 against; the force of the spring. This completes thecircuit and the tool is rotated through. the connection described.

If it is desired to maintain the tool in. operationwithout the necessityof continued finger pressureupon the trigger member 5, the operator, as.by-theuse of the first finger of his hand, or by the slight upward.movement of the same finger which is pressing upon trigger member 5,can: press. up. the pivoted detent lever 6: shown in- Figs. 5 and 7.;This lever is carried by the screw 45, tapped? into the under face ofthe frame section I, and rocks up and down uponthe spherical inner face46' of the screw head as shown. Spring 41 tendstothrow this detent intothe inactive position shown in Fig. 5. When the trigger i'sheld back bythe finger of the operator into. the power supply position as shown inFig. '7 and the detent is pushed up against the action of the spring ilby the same or another finger of'the same hand of the operator, theinner end of the detent slightly incline-das at 48 is-brought to.position against the edge d3 of. the cut out in the trigger 51 alsoslightly inclined. and the parts will behcldin that position until. theoperator releases the loci; by again pressing in slightly. on thetrigger so. that the trigger lock may automaticallyresume, the; positionshown in- Fig. 5.

It; will thus be,- scen that there is provided: an. of? and onswitch.which may be readily operated byrt he finger; one hand and at: thesametime be; locked positio so long as desired by the slight movement ofthe; same; or another fingerof the same hand or the operator and this.lock a in; ased: wh n. sir d.

In. E s to- 1: 5.- is; shown. another form of lock:

locking lever 50 is shown mounted for simple horizontal pivotingmovement about the screw 51 tapped into the frame. This lever when inits intermediate position as shown in Fig. 12 has no effect upon theswitch trigger. When, however, the switch trigger is retracted to theposition shown in Fig. 13 the operator by turning, with his finger, thelocking lever 50 in either direction may lock it against either one ofthe faces 52 of the end cut out on the top of the switch trigger.

Figs. 14 and 15 show a detent lock same as that shown in Figs. 11, 12and 13 but there is also provided a leaf spring 53 seated at one end inthe frame at 54 normally tending to hold the locking lever in itscentral non-active position. In this case the lever is thrown to thelocking position by the finger of the operator against the force of thisspring, which will without action of the operator return the lock tonegative position when the switch trigger is retracted.

The efiiciency of the outside assembly form of the casing constructionas shown in Figs. 1 and has been sufficiently referred to.

Thi construction, however, has a further advantage in the form andarrangement of casing sections in that it permits a ready insertion ofinterior working units followed by completion of casing assembly and anequally ready removal of the parts for repair, replacement or any otherpurpose. Referring on this point to Fig. 5, it will be seen that theinterior motor assembly in the main section of the casing can beinserted as a unit, thereafter the two brush units put in place, theconnecting section C of the frame added, and the casing section B andthe chuck driv parts carried thereby added as a unit. Thereupon, theassembly is completed by positiom'ng the lower hand grip section D shownin Fig. 8 in position such that the leads 58 and 59 can be readilyconnected to their screw contact posts and thereupon this sectioncarried up to the position shown in Fig. 5 and held there by screw 55.

The entire tool may be thus assembled or disassembled with a minimum ofeffort and when assembled it shows marked efliciency in operation andlimited likelihood of breakdown in use.

Since certain changes may be made in the above construction anddifferent embodiments of the invention could be made without departingfrom the scope thereof, it is intended that all matter contained in theabove description or shown in the accompanying drawing shall beinterpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which as amatter of language might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

1. In an electric tool a brush adapted to bear at its end upon acommutator and extended from said bearing content along a circular arcand at its farther end approaching the commutator at a point along thecircumference thereof from said bearin contact area, and a coil springhaving an arm extended therefrom bearing against the farther end of thebrush to impose a spring pressure upon the are shaped brush to feed itto the armature contact area as it is worn.

2. In an electric tool a brush adapted to hear at its end upon acommutator and extended from said bearing contact along a circular arcand at its farther end approaching the commutator at a point along thecircumference thereof from said bearing contact area, and a coil springhaving an arm extended therefrom bearing against the farther end of thebrush to impose a continuous and even spring pressure upon the areshaped brush to feed it to the armature contact area as it is worn, astop for said spring, in position, at the end of its feeding'stroke, toprevent contact thereof with the commutator.

3. In an electric drill, a brush assembly unit comprising an are shapedholder, an arc shaped brush carried thereby, spring means acting to feedsaid brush from said holder and a springpressed brake operating throughan opening in said brush holder upon the brush to retain it within theholder.

4. In an electric tool a brush assembly unit, comprising an are shapedholder, an are shaped brush carried thereby, a spring tending to feedsaid brush through the said holder, a springpressed brake operatingthrough an opening in said brush holder upon the brush at a point adja-'cent its contact area end, and means for holding said brake out ofaction when the brush assembly unit is in operative position within thetool.

5. In a brush assembly unit, a holder, are shaped for the reception ofan are shaped brush, a portion of said holder being cut away to permitthe insertion of one end of the arc shaped brush within such cut awayportion.

6. In a brush assembl unit, an arc shaped brush holder, an arc shapedbrush, the material of said holder being cut away at one side to providean opening such that the end of the brush may be inserted in saidopening from the side.

7. In a brush assembly unit, an are shaped brush, an are shaped brushholder, said brush having a contact area at one end therefor, a

, spring bearing upon the other end of said brush to feed it to thecommutator, a section of the holder being cut away so that the brush canbe inserted from the side and the brush then moved, carrying the springwith it and putting tension upon the spring until the brush is inposition for use.

8. In a brush assembly unit, an are shaped brush, an are shaped brushholder, saidbrushhaving a contact area at one end therefor, a springbearing upon the other end of said brush to feed it to the commutator, asection of the holder being cut away so that the brush can be insertedfrom the side and the brush then moved, carrying the spring with it andputting tension upon the spring until the brush is in position for use,and a brake adapted to bear against said brush to hold it in positionwithin the commutator as against the pressure of said spring.

9. In a brush assembly unit, an arc shaped brush, an arc shaped brushholder, said brush having a contact area at one end therefor, a springbearing upon the other end of said brush to feed it to the commutator, asection of the holder being cut away so that the brush can be insertedfrom the side and the brush then moved, carrying the spring with it andputting tension upon the spring until the brush is in position for use,and a spring-pressed brake adapted to bear against said brush to hold itin position within the commutator as against the pressure of saidspring.

FRANCESCO COLLURA.

(References on following page) um er REFERENCES CITED 2,277,572 Thefollowing references are of record in the 2,349,401 file of this patent:2,373,842 5 2,389,941 UNITED STATES PATENTS 2,399,935 Number Name Date731,740 Bassett June 23, 1903 2,029,171 Lundquist Jan. 28, 1936 Number2,234,695 Hanna Mar. 1 19 1 10 269,203

Name Date Weissinger Mar. 24, 1942 Beckwith May 23, 1944 Mitchell Apr.1'7, 1945 Stephenson Nov. 27, 1945 Merrill May '7, 1946 FOREIGN PATENTSCountry Date Italy Nov. 13, 1929

